RH4 To Narley Port Conversion Tubes

Fast Eddie said:

This is the velocity graph below.

What I can tell you is that this work yielded a 9 (yes NINE) rwhp increase on this particular engine set up.

Old news though, well worth reading through Comnoz’ head flow testing thread if you’re interested in this stuff.

Click to expand...

Air speed is better on the stock RH10 than I thought it would be. 9whp is a lot going into that 20cfm. Which is to the point that it is not all CFM, I suspect the larger valve size removes a bottleneck.

Fast Eddie said:

This is the velocity graph below.

What I can tell you is that this work yielded a 9 (yes NINE) rwhp increase on this particular engine set up.

Old news though, well worth reading through Comnoz’ head flow testing thread if you’re interested in this stuff.

View attachment 116739

Click to expand...

If it was ported then its larger than 30mm now. Can you say how much larger it is and where?

Yes porting is very important. I sent some modified Axtell port specs to a 500 cc racer in the UK and he found a 7 hp increase (same size valves).

Brian's 500 (pre 1950 class)

jseng1 said:

If it was ported then its larger than 30mm now. Can you say how much larger it is and where?

Yes porting is very important. I sent some modified Axtell port specs to a 500 cc racer in the UK and he found a 7 hp increase (same size valves).

Brian's 500

Click to expand...

Still 30mm Jim (like I clearly stated). Work was done around the valve throat only.

jseng1 said:

If it was ported then its larger than 30mm now. Can you say how much larger it is and where?

Yes porting is very important. I sent some modified Axtell port specs to a 500 cc racer in the UK and he found a 7 hp increase (same size valves).

Brian's 500 (pre 1950 class)

Click to expand...

As far as speed is concerned, weight distribution can be more important than horsepower. If the front feels light, it will deter you from accelerating earlier when in corners.